Question
Show that $1+\text{i}^{10}+\text{i}^{20}+\text{i}^{30}$ is a real number.

Answer

$1+\text{i}^{10}+\text{i}^{20}+\text{i}^{30}=1+\text{i}^{4\times2}\times\text{i}^2+\text{i}^{4\times5}+\text{i}^{4\times7}\times\text{i}^2$

$=1+1\times\text{i}^2+1+1\times\text{i}^2$

$=1-1+1-1$

$=0,$ which is real number.

Need a full question paper?

Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.

Start Generating Free